The present invention relates to an inlet valve assembly for a central vacuum system and, in particular, to a mechanism for securing the valve assembly to a wall or floor.
Central vacuum systems may be installed in new construction or in existing houses. Such systems have a number of inlet valves mounted throughout the house on various walls and floors. Each of these inlet valves connect to a central vacuum by means of a network of pipes or hoses.
The inlet valves often consist of (1) a face plate with a door and an inlet tube, and (2) a rear backer plate carrying a larger adaptor tube that telescopically fits around the inlet tube in the face plate. A system connection can be made to the tube on the backer plate. For examples of inlet valves see U.S. Pat. Nos. 2,851,286; 3,088,484; 4,688,596; and 4,758,170.
In new construction the rear backer plate is often mounted on a stud and then a matching hole is cut in the dry wall about to be installed. After the dry wall is installed, the front face plate can be mounted over the hole in alignment with the backer plate.
When installing a valve in existing homes, the backer plate is normally not attached to a stud. Instead, the installer relies on the fact that the backer plate is larger than the hole made in the wall or floor for the valve. After cutting this hole the installer will insert the shorter end of the backer plate edgewise into the hole. Once past the dry wall, the backer plate is turned by hand so it lies flat against the backside of the dry wall. Typically then, a hook or other fixture is used to hold the backer plate in position, while the front plate is then slipped over the outside end of the hook to lie against the outside of the wall in line with the backer plate. Holding the hook with one hand, the installer must now drive screws through the face plate, the dry wall and into the backer plate. This operation obviously requires much manual dexterity and the difficulty in aligning the face plate and backer plate is apparent.
Regardless of the care taken by the installer, the face plates of these known valves often do not have a visually "correct" alignment with the room structure. Before insertion into a wall, the backer plate's tube usually has glued to it a fitting such as an elbow. Being glued first, the elbow and therefore the backer plate and face plate will have a strictly defined orientation to the pipe that will eventually connect to the elbow. Since the face plate is committed to a particular orientation, it cannot be later readjusted to compensate for small misalignments. Virtual misalignments may also occur when the floor and walls are not plumb and square. Thus a face plate may be truly vertical but appear tilted because the wall or floor is not true. The need for such offsetting adjustments are extremely difficult to anticipate before the face plate is in place, after which readjustment is impossible with conventional valves.
Another disadvantage with known inlet valves is the fact that the junction between the tubes of the face plate and backer plate is discontinuous, thereby creating turbulence and an opportunity for clogging. Also, the joint between these tubes normally employs an O-ring that can leak as the ring drys over time.
Conventional valves are also unable to accommodate the great variety of types of central vacuum systems. One common central vacuum system employs a pair of low voltage, metal contacts that protrude into the cylindrical inlet of the valve. The insertion into the inlet valve of the metal fitting of a vacuum hose shorts those contacts to start the central vacuum pump. Alternatively, the hose coupling may have semi-cylindrical conductive halves that separately connect to the valve contacts and to a remote switch at the operating end of the hose, so the vacuum system can be turned on and off remotely. Other types of vacuum systems supply a higher voltage to a receptacle on the face plate so that a separate electrical plug on the proximal end of the hose can power equipment such as a rug beater at the remote end of the hose. To accommodate different system types, known valves have used a knockout plate for optional installation of such a receptacle.
Some systems provide low voltage, door switches to start the vacuum system. Some of these systems will positively start the central vacuum, even in the absence of an inserted hose, when the door is opened to an extreme position. Other systems start the vacuum as soon as the door is opened even slightly. Still other valves use a higher voltage microswitch that is activated either when the valve door is lifted, or upon the insertion of a hose.
Known valves have been dedicated to one of the foregoing system types. No known valves, however, have been able to accommodate a significant number of the varieties of systems. Accordingly, an installer must carry a large inventory of valves in order to install the various types of systems requested by homeowners.
Known electrical outlet boxes have wings or tabs that are initially stowed close to the box so they can be inserted into a dry wall. Once inserted, the wings or tabs are rotated by screws through a plane parallel to the dry wall, from a position alongside the box to a position extending behind the dry wall. After such extension, the screws can be tightened to press the wing or tab against the back of the dry wall. See for example U.S. Pat. Nos. 2,320,400; and 2,801,019. See also U.S. Pat. No. 3,018,082, showing a bracket arm rotating about an axis perpendicular to a ceiling for mounting a light fixture.
Other electrical boxes have wings or tabs that are located inside the electrical box and are rotated out of the box and behind the dry wall, all for similar purposes. See for example U.S. Pat. Nos. 2,031,861; 2,413,139; and 2,875,914. Still other electrical boxes use flaps that fold flat against the electrical box but unfold when pushed past the dry wall. These flaps rotate on an axis that is parallel to the dry wall. See, for example, U.S. Pat. Nos. 1,775,665; and 1,957,003. See also U.S. Pat. Nos. 4,304,958; and 4,332,330.
In U.S. Pat. No. 3,322,442 a cylindrical insert is connected to a duct by inserting its lower collar into a circular opening in the duct. A ledge on the insert keeps it from falling into the duct. Clamps are then rotated from a position inside the cylindrical insert to a position outside, to clamp the cylindrical insert onto the duct wall. See also U.S. Pat. No. 4,023,833.